I have a dislike for museums and art galleries that disallow photos to be taken of the space and artwork. I understand it's to protect the artwork from being illegally duplicated and sold, however, the intent of any exhibition is to show off the work, then having photos taken of it to be shared with the world should serve as free publicity that draws attention to the artist, the artwork, and of course the museum or gallery.
To see a glimpse of what this exhibit about while I comment on it as it pertains to my thoughts and understanding as it pertains to my research, please search "Walter de Maria Broken Kilometer" on Google Images.
As described by the Dia Art Foundation flyer, the Broken Kilometer is composed of 500 highly polished, round, solid brass rods, each measuring two meters in length and five centimeters in diameter. The rods are placed in five parallel rows of 100 rows each. The sculpture weighs 18-3/4 tons and would measure 3,280 feet if all the elements were laid end to end. Each rod is placed such that the space between the rods increase by 5 millimeters with each consecutive space, from front to back; the first rods of each row are placed 80 millimeters apart, the last two rods are placed 580 millimeters apart. Metal halide stadium lights illuminate the work, which is 45 feet wide and 125 feet long. There is a companion piece in Kassel, Germany called "Vertical Earth Kilometer" - A brass rod of the same diameter, total weight, and totally length has been inserted 1,000 meters into the ground. It was installed in 1977, two years before the Broken Kilometer.
From a materials perspective, without knowing the total tonnage of the sculpture, I could imagine how heavy each one of these rods must feel. I did not notice the change in spacing as I looked towards the back, but I did wonder how far away from the viewing position could the artist have replaced those brass rods with some kind of substitute that looked exactly the same?